Rodolfo Coria stands in front of Argentinosaurus, the largest-known creature ever to walk the earth

I spent several days riding around the desert with Calvo to the village museums he had established. He allowed me to participate with his crew in the digging up of a new sauropod dinosaur in his latest fossil quarry beside Lake Barreales.

Finding new dinosaurs and their contemporary flora and fauna is clearly Calvo’s raison d'être. He doesn’t have field seasons; he lives at his most productive site all year round, using it as a home base from which to truck out to find dinosaur fossils and tracks in other locales, too. Other work—his university teaching duties and his entrepreneurial work to attract tourists to the museums—is a necessary evil to fund this passion. English is not his first language, but his enthusiasm for discovery bubbled through our language barrier when told me: “I think the most important finding that I do with my life is I find a lot of fossils.”

A lot, indeed. And arguably the southern hemisphere’s most important to science since the records set by his mentor, José Bonaparte, the “father of Argentine paleontology.” Early in his career, Calvo directed one of the two teams that excavated and cleaned the fossils of the largest creature ever to walk the earth: the sauropod dinosaur Agentinosaurus. Everyone thought that Bonaparte would co-write the paper with Calvo. But because of Calvo’s youth, Bonaparte decided at the last minute to instead co-write the description with his illustrator, Rodolfo Coria, whom he brought down to the province after most of the work had been done. Coria received the credit and all the subsequent publicity that went with this discovery.

Calvo also found and published the first specimen belonging to the largest known carnivore ever to walk the earth, a giant T-Rex-like theropod dinosaur, but his rival, Coria, was credited once again with finding the holotype, that is, the type specimen, when he later found another, more complete skeleton and published the creature as Giganotosaurus carolinii in Nature. Credited with both the largest herbivore and the largest carnivore, Coria achieved worldwide celebrity, appearing on a number of television programs in the U.S. He touted his “new” theropod as, “probably the world’s biggest predatory dinosaur”—though Calvo’s earlier discovered specimen belonged to an animal that was actually about eight percent larger.

More important, Calvo made key contributions to our understanding of the branching history of dinosaur groups—particularly the giant sauropods, the long-necked, long-tailed, pin-headed, quadrupedal herbivores. Textbooks declared that sauropods became rare toward the end of the Cretaceous. Bonaparte and his disciple Calvo brought enough specimens to light to show that the sauropods actually enjoyed their heyday at this time—but it was in the south, in the form of the giant titanosaurs. Though they were initially distributed over every continent, the southern titanosaurs became the only remaining sauropods by the Late Cretaceous, when all others became extinct. When the supercontinent Pangea broke up into Laurasia in the north and Gondwana in the south, the titanosaurs became the most abundant dinosaur in Gondwana. However, until recent decades, titanosaur specimens around the southern hemisphere were limited to relatively incomplete skeletons—thus creating a confused phylogeny (the evolutionary history of a group of organisms).

Normally, it takes a marine environment to preserve an entire ecosystem from one time interval; sediments at Barreales were deposited by a series of meandering rivers and lakes that, at least for one 90-million-year-old snapshot, preserved an exceptional sampling of everything that was buried along the banks, including leaves and many soft tissues.

Calvo and a grad student inspect a titanosaur femur propped up at Lake Barreales.

Calvo has been a decisive player in rebuilding that titanosaur tree, co-publishing the earliest known titanosaur, Andesaurus delgadoi, whose foundational traits are now used to identify all titanosaurs. His numerous discoveries and descriptions of other dinosaurs culminated with his re-classification of many taxa within both the sauropod and theropod family trees. Collaborating with others, he measured and counted the number of anatomical traits in a long list of taxa (cladistic analysis), changing earlier views of which animals were most closely related to which.

Calvo didn’t find the largest titanosaur, but he did find the most complete one. His discovery of Futalognkosaurus dukei at Lake Barreales has given the world its largest, most complete specimen of a titanosaur (70 percent complete, compared to the 10 percent complete Argentinosaurus, the largest known animal to have walked the earth, credited to his rival, Coria.). Futalognkosaurus gives scientists the necessary gauge to make accurate estimates of how large other, less complete titanosaurs were. And recently, Calvo co-published tracks of the last known dinosaurs before the great dino extinction 66 million years ago.

But the thing that really gets Calvo excited is when you get him talking about his greatest find, the discovery he is now devoting his life to: not just a new dinosaur site: but a reservoir of fossils of every kind of life from the same time period, exquisitely preserved, the rarest of fossil gold mines, known by paleontologists as a Fossillagerstätte. The Lake Barreales site is not only crowded with fossils—it represents a “day in the life” of our planet 90 million years ago. “This excavation I think is the most exciting thing,” he says, “because it’s not just a dinosaur, two dinosaurs, it’s all the life …. I think it’s the only place in the world where we have plants and fish and turtles and dinosaur eggs and pterosaurs and crocs and every fauna.” Now we know exactly what kinds of flowering plants and leaves were available for the giant herbivores to eat.

Normally, it takes a marine environment to preserve an entire ecosystem from one time interval; sediments at Barreales were deposited by a series of meandering rivers and lakes that, at least for one 90-million-year-old snapshot, preserved an exceptional sampling of everything that was buried along the banks, including leaves and many soft tissues.

I asked Calvo what criteria he used to help him decide which areas were most promising to search for dinosaur fossils. No criteria needed here, he said. “I live in an area full with dinosaurs. If I move anywhere, I can find dinosaur.”

In the surrounding locales, he says, prospectors feel lucky if they find a dinosaur within twenty kilometers of another. And those they find come from many different time periods, revealing nothing about which dinosaurs lived contemporaneously. “If you work in the same area for too much time,” Calvo says, “you will find the same species—that’s common. Here each time that we go to the field we find something new.”

But even outside the Barreales area, he says, dinosaur hunters are collecting lots of fossils in Patagonia every year. There are plenty to go around for all the paleontologists, including his rival. “So there is no problem with competing with him for the size of a dinosaur,” Calvo says. “I’m just working and I am fine and good in Barreales, because I love this place, and I love my job.”

A few days later, I was again standing beside my little red-dust covered Chevy Corsa in the middle of the desert. This time, the engine had stalled and I’d found the last drops of gas dripping below the car. The fuel pump had been gashed by one of those stones that flew up while I was driving over them—maybe faster than I should have been. It was starting to rain and getting dark, and I was once again wishing I’d packed a warm coat.

So, I wanted to know, how was I going to get out of the desert in time to keep my morning appointment with Calvo’s rival, Rodolfo Coria, in Plaza Huincul, and then the next day with their mentor, José Bonaparte, up near Buenos Aires? Should I start walking? Or would the Lord provide by some means beyond my present imagination? Calvo had raised so many questions for me about dinosaur evolution that I wanted to ask these guys. Would I ever get to ask them?

Answers of this sort, the kind most worth going after, don’t come in an instant—or without a little trouble. It took most of the night, but after a passerby let me use his cell phone to call Hertz, and after Hertz searched for hours for me and gave up (I wasn’t the only one who had trouble finding this spot in the desert), I got a ride to a town that Hertz could find. And from there I drove in my replacement rental to the town where I had a morning appointment with Rodolfo Coria. There was little time to spare, even for sleep, and I wasn’t sure how well I’d be able to focus on all those important questions I wanted to ask him.

Once again, the one thing I could be sure of was that my heart was in this little adventure and in my quest for this knowledge, much more than my heart had been in any other kind of work I’d ever done.

Such enthusiasm isn’t exactly discouraged by my travel Guide: “Whatever you do, work at it with all your heart, as working for the Lord, not for human masters” (Colossians 3:23).

With or without that Guide, many of this world’s scientist-adventurers have found greatest fulfillment when living according to its instruction:

“Whatever your hand finds to do, do it with all your might” (Ecclesiastes 9:10).